1. Field of the Invention
The present invention relates to a double-combustor type pulsating combustion apparatus for combusting a pair of pulsating combustors in reverse phase to each other.
2. Description of the Related Art
A coupling type pulsating combustion apparatus which solves a problem of noise of the defect of a pulsating combustion apparatus using one pulsating combustor is known. The apparatuses of this type are disclosed, for example, in U.S. Pat. Nos. 4,840,558 and 4,917,596. The apparatus of this type ordinarily comprises, in addition to a pair of combustion chambers formed in the same arrangement for combusting mixture gas of fuel and combustion air in a pulsating manner, tail pipes connected to the exhaust ports of the combustion chambers for exhausting exhaust gases, air-intake pipes connected at one end to the air-intake ports of the combustion chambers for supplying air necessary for combustion to the combustion chambers, an air-intake chamber connected commonly at the other end of the air-intake pipes, an exhaust chamber connected commonly at the downstream side of the tail pipes, aerodynamic valves provided in the air-intake pipes, having larger backward flow efficiency than forward flow efficiency, a fuel-supplying system for supplying fuel between the aerodynamic valves and the air-intake ports in the air-intake pipes, ignitors provided in the combustion chambers for igniting the mixture gas supplied into the combustion chambers at the time of starting, and an air-supplying fan having a small capacity, provided in or at the upstream side of the air-intake chamber.
In the coupling type pulsating combustion apparatus in which the aerodynamic valves are interposed in the air-intake pipes, the pressures in the two combustion chambers can be strongly interfered through two aerodynamic valves. Thus, the oscillating periods of the pulsating combustors can be differentiated at 180 degrees to reduce its noise.
As disclosed in U.S. patent application Ser. No. 437,187, now U.S. Pat. No. 4,946,381, filed by the inventors including ones of the present invention, a combustion amount can be varied to approx. 1/3 of the maximum combustion amount by varying the rotating speed of the air-supplying fan in response to the supplying amount of fuel at the time of operation.
However, when the coupling type pulsating combustion apparatus disclosed as above is applied, for example, for a domestic room heater, a request for further reducing room heating capacity is strongly desired due to advancement in high heat insulation and high density in residence. However, in the apparatus described above, the request for the further reduction in the room heating capacity cannot be coped with the combustion amount of approx. 1/3 of the maximum combustion amount.
In order to reduce the combustion amount to 1/3 or less of the maximum combustion amount, a method of controlling on/off a coupling type pulsating combustion apparatus is, for example, considered. However, in this manner, there arise problems of repetitive thermal stress, increase in CO concentration in combustion gas, and frosting due to condensation in a coupling type pulsating combustion apparatus by frequent on/off of a solenoid valve.
That is, in the conventional coupling type pulsating combustion apparatus, the varying range of the combustion amount cannot be reduced to 1/3 or less of the maximum combustion amount, and it cannot be applied to an equipment necessary for a large capacity varying range for domestic room heaters, etc.